Scaling and Resonances in Elementary K^+ Lambda Photoproduction

TL;DR

This paper investigates scaling behaviors and resonance structures in K^+ Lambda photoproduction, revealing consistent scaling across regimes and identifying key nucleon resonances influencing the reaction dynamics.

Contribution

It demonstrates that the reaction exhibits scaling in both low-t Regge and high-energy constituent counting regimes, and identifies specific N^* resonances affecting the process.

Findings

Scaling holds in both low-t and high-energy regimes.

Strong evidence for s-channel resonances below W=2.3 GeV.

Identification of key nucleon resonances at 1690, 1920, and 2100 MeV.

Abstract

Recent cross section data for the reaction gamma + p \to K^+ + Lambda are examined for evidence of scaling in both the low-t Regge domain and in the high \sqrt{s} and -t domain where constituent counting may apply. It is shown that the reaction does scale in both regimes. At large center of mass angles, s^{-7} scaling appears to hold at essentially all -t, but with angle-dependent oscillations. The scaled data show particularly strong evidence for s-channel resonances for -t below 2 GeV^2 and for W below about 2.3 GeV. The dominant contributions are consistent with an N^* S_{11} resonance at 1690 MeV, a P_{13} at 1920 MeV, and a D_{13} resonance at 2100 MeV, which interfere to give the observed strong angular dependence.